1. Field of the Invention
The field of this invention is directed to metal detection devices and more particularly to a metal detection device which is to be directly mounted on a human hand.
2. Description of the Prior Art
Metals have one important property possessed by no other elements that enables such to be readily distinguished with suitably sensitive apparatus. This property is their high electrical conductivity. By generating an alternating magnetic field in the vicinity of a metal object, electric currents are induced in the object which in turn set up a magnetic field around the object which distorts the original field. By detecting this distortion, the metal object can be located.
One common type of metal detector is deemed a pulse magnetization unit. Pulse magnetization units rely on the fact that a magnetic field takes a finite time to propagate through air or earth. The speed of propagation is the same as for electromagnetic radiation, that is, the speed of light. Such units operate as magnetic "radar" units. A short, high-powered pulse is generated in a search coil, and after the pulse is cut off, the unit goes from a transmit mode to receive mode. If there is a metallic object within the field, this object generates its own magnetic field by the process of induced magnetism, and this is detected a finite time after the transmitted pulse. Such metal detectors are used to detect coins, jewelry and any metallic object on beaches, parks and other places common to the usage by humans. Some people have made it a hobby to use such metal detectors to discover such lost metallic objects.
However, metal detectors are also used as stationary units within airports. The purpose of the stationary metal detector is to detect the presence of a dense metallic object on a person before that person enters an airplane either as a passenger or a crew member. Metal detectors are also used as portable units which can be readily carried by a person. These portable units are the detectors that are used to detect the presence of metal within areas, such as beaches and parks, that are frequently used as places of congregation by people.
Within the field of law enforcement, portable metal detectors are commonly used to detect the presence of metallic objects on a person that is subject to detainment. Normally, the metallic object that is being looked for is a knife or a gun. Typically, such metal detectors are in the shape of a "wand". This wand comprises a hand graspable cylindrical object, usually about ten inches in length, that is intended to be moved in close proximity to the person that is being examined. Upon a metal object being detected, the metal detector will activate an annunciator which can be in the form of a vibrator, a light or a buzzer. The metal object can then be removed from the person that is being examined.
One problem with such a wand type of annunciator is that it requires that one hand of the operator be used to operate the metal detector. In law enforcement, it would be preferable to use a metal detector which did not require the entire usage of ones hand thereby leaving that hand free to perform other tasks such as permit the physical grasping of a discovered metallic object. It may also save a law enforcement officer's life to have available both hands to counter a physical accostation rather than having one hand occupied.